Snare

ABSTRACT

An intravascular snare device for use in capturing debris found in blood vessels. The snare device is fabricated from a tube and includes longitudinally and circumferentially extending members. The snare device specifically embodies structure that provides enhanced radial opening and angular resistance to collapse.

This application is a divisional of U.S. application Ser. No.10/123,896, filed Apr. 15, 2002, now U.S. Pat. No. 6,592,607; which is acontinuation of U.S. application Ser. No. 09/469,431, filed Dec. 23,1999, now U.S. Pat. No. 6,402,771.

BACKGROUND OF THE INVENTION

The present invention relates generally to intravascular snare devicesand systems and more particularly, devices which can be used to captureembolic material or thrombi found in blood vessels.

The intravascular snare device and system of the present invention isparticularly useful when performing balloon angioplasty, stentingprocedures, laser angioplasty or atherectomy in critical vessels wherethe release of embolic debris into the bloodstream can occlude the flowof oxygenated blood to the brain or other vital organs, which can causedevastating consequences to the patient. The snare device is also suitedfor the removal of clots adhering to vessel walls. While the snaredevice and system of the present invention is particularly useful in thecerebral vasculature and neurovasculature, the invention can be used inconjunction with any vascular interventional procedure in which there isan embolic risk.

A variety of non-surgical interventional procedures have been developedover the years for opening stenosed or occluded blood vessels in apatient caused by the build up of plaque or other substances on the wallof the blood vessel. Such procedures usually involve the remoteintroduction of the interventional device into the lumen of the artery,usually through a catheter. In typical carotid PTA procedures, a guidingcatheter or sheath is percutaneously introduced into the cardiovascularsystem of a patient through the femoral artery and advanced, forexample, through the vasculature until the distal end of the guidingcatheter is in the common carotid artery. A guidewire and a dilatationcatheter having a balloon on the distal end are introduced through theguiding catheter with the guidewire sliding within the dilatationcatheter. The guidewire is first advanced out of the guiding catheterinto the patient's carotid vasculature and is directed across thearterial lesion. The dilatation catheter is subsequently advanced overthe previously advanced guidewire until the dilatation balloon isproperly positioned across the arterial lesion. Once in position acrossthe lesion, the expandable balloon is inflated to a predetermined sizewith a radiopaque liquid at relatively high pressures to radiallycompress the atherosclerotic plaque of the lesion against the inside ofthe artery wall and thereby dilate the lumen of the artery. The balloonis then deflated to a small profile so that the dilatation catheter canbe withdrawn from the patient's vasculature and the blood flow resumedthrough the dilated artery. As should be appreciated by those skilled inthe art, while the above-described procedure is typical, it is not theonly method used in angioplasty.

Another procedure is laser angioplasty which utilizes a laser to ablatethe stenosis by super heating and vaporizing the deposited plaque.Atherectomy is yet another method of treating a stenosed blood vessel inwhich cutting blades are rotated to shave the deposited plaque from thearterial wall. A vacuum catheter is usually used to capture the shavedplaque or thrombus from the blood stream during this procedure.

In the procedures of the kind referenced above, abrupt reclosure mayoccur or restenosis of the artery may develop over time, which mayrequire another angioplasty procedure, a surgical bypass operation, orsome other method of repairing or strengthening the area. To reduce thelikelihood of the occurrence of abrupt reclosure and to strengthen thearea, a physician can implant an intravascular prosthesis formaintaining vascular patency, commonly known as a stent, inside theartery across the lesion. The stent is crimped tightly onto the balloonportion of the catheter and transported in its delivery diameter throughthe patient's vasculature. At the deployment site, the stent is expandedto a larger diameter, often by inflating the balloon portion of thecatheter.

Prior art stents typically fall into two general categories ofconstruction. A first type of stent is expandable upon application of acontrolled force, as described above, through the inflation of theballoon portion of a dilatation catheter which, upon inflation of theballoon or other expansion means, expands the compressed stent to alarger diameter to be left in place within the artery at the targetsite. A second type of stent is a self-expanding stent formed from, forexample, shape memory metals or super-elastic nickel-titanum (NiTi)alloys, which will automatically expand from a compressed state when thestent is advanced out of the distal end of the delivery catheter intothe body lumen. Such stents manufactured from expandable heat sensitivematerials allow for phase transformations of the material to occur,resulting in the expansion and contraction of the stent.

The above minimally invasive interventional procedures, when successful,avoid the necessity of major surgical operations. However, there is onecommon problem which can become associated with all of these types ofprocedures, namely, the potential release of embolic debris into thebloodstream that can occlude distal vasculature and cause significanthealth problems to the patient. For example, during deployment of astent, it is possible that the metal struts of the stent can cut intothe stenosis and shear off pieces of plaque which become embolic debristhat can travel downstream and lodge somewhere in the patient's vascularsystem. Pieces of plaque material can sometimes dislodge from thestenosis during a balloon angioplasty procedure and become released intothe bloodstream. Additionally, while complete vaporization of plaque isthe intended goal during a laser angioplasty procedure, quite oftenparticles are not fully vaporized and thus enter the bloodstream.Likewise, not all of the emboli created during an atherectomy proceduremay be drawn into the vacuum catheter and, as a result, enter thebloodstream as well.

When any of the above-described procedures are performed in the carotidarteries, cerebral vasculature, or neurovasculature, the release ofemboli into the circulatory system can be extremely dangerous andsometimes fatal to the patient. Naturally occurring debris can also behighly dangerous to a patient. That is, debris which travels through theblood vessel as a natural result of bodily functions and not as a resultof an intervention procedure. Debris that is carried by the bloodstreamto distal vessels of the brain can cause these cerebral vessels toocclude, resulting in a stroke, and in some cases, death. Therefore,although cerebral percutaneous transluminal angioplasty has beenperformed in the past, the number of procedures performed has beenlimited due to the justifiable fear of causing an embolic stroke shouldembolic debris enter the bloodstream and block vital downstream bloodpassages.

Medical devices have been developed to attempt to deal with the problemcreated when debris or fragments that naturally occur or that enter thecirculatory system following vessel treatment utilizing any one of theabove-identified procedures. One approach which has been attempted isthe cutting of any debris into minute sizes which pose little chance ofbecoming occluded in major vessels within the patient's vasculature.However, it is often difficult to control the size of the fragmentswhich are formed, and the potential risk of vessel occlusion stillexists, making such a procedure in the carotid arteries a high-riskproposition.

In addition, the retrieval of fragmented clot may be incomplete, alsoresulting in emboli and distal occlusions, and further, access throughtortuous lumens may prove difficult. Laser-based disruption devicesemploy the photo-acoustic effect to fragment clot. Local disruption mayopen up a proximal occlusion but also may cause significant distalemboli.

Other techniques which have been developed to address the problem ofremoving embolic debris include the use of catheters with a vacuumsource which provides temporary suction to remove embolic debris fromthe bloodstream. However, as mentioned above, there have beencomplications with such systems since the vacuum catheter may not alwaysremove all of the embolic material from the bloodstream, and a powerfulsuction could otherwise cause problems to the patient's vasculature.Other techniques which have had some limited success include theplacement of a filter or trap downstream from the treatment site tocapture embolic debris before it reaches the smaller blood vesselsdownstream. However, there have been problems associated withconventional filtering systems as well. In particular, certainpreviously developed filtering devices do not optimize the area forembolic collection. That is, conventional filtering devices may notpresent a collection device that spans the entity of the vessel or itmay include supporting structure that itself impedes emboli collection.Certain other devices do not embody sufficient angular resistance tocollapse.

Moreover, thrombectomy and foreign matter removal devices have beendisclosed in the art. However, in addition suffering from the samedisadvantages as certain conventional filter devices, such devices havebeen found to have structures which are either highly complex or lackingin sufficient or effective expansion and retraction capabilities.Disadvantages associated with the devices having highly complexstructure include difficulty in manufacturability as well as use inconjunction with microcatheters. Other less complex devices can pullthrough clots due to in part to the lack of experience in using the sameor otherwise lack an expanded profile that is adequate in capturingclots or foreign bodies.

Furthermore, in current interventional radiology practice, the needarises to remove a variety of objects from intraluminal spaces. Amongthese are embolic coils, guidewire tips, distal catheter segments,thrombus and other vascular emboli, few of which can be readily removedwith current devices. Thrombo-embolic materials can be friable,amorphous, and/or lubricious in nature contributing to this difficulty.Most current therapies rely on grasping, fragmenting, or dissolving theblood-based obstructions. Among the grasping devices are the loop snaresand the wire basket snares. These devices may have limitedeffectiveness, due in part to the lack of encapsulation. Objects aredifficult to grasp within these devices, and friable objects, e.g.blood-based blockages, tend to fragment when grasped or pulled,introducing multiple emboli.

Lytic drugs are also used to dissolve blood-based obstructions. Thesetypically have the disadvantages of lengthy treatment/infusion times toremove the obstruction (>3 hrs.), production of emboli, and thepotential for systemic iatrogenic bleeding as a side effect of the drugusage. Also, these drugs are not typically effective in removingobstructions that are not blood-based.

What has been needed is a reliable intravascular snare device and systemfor use when treating blood vessels. The snare devices should be capableof capturing any naturally occurring embolic debris or that which may bereleased into the bloodstream during an interventional treatment, whileminimizing the area occupied by structure supporting the device, andsafely containing the debris until the snare device is removed from thepatient's vasculature. The devices should embody an expanded profilethat presents a consistent radial opening that completely occupies thevessel at the repair site as well as structure for effectively resistingcollapse. Moreover, such devices should be relatively easy to deploy andremove from the patient's vasculature and also should be capable ofbeing used in narrow and very distal vasculature such as the cerebralvasculature. The following invention addresses these needs.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed towardssnares for removing undesired material or objects and restoring patencyof blood vessels. The snare is a linked or monolithic framework of thinstruts that is radially expansible. The snare of the present inventionembodies a structure that provides a consistent radial opening as wellas improved radial and angular resistance to collapse. That is, as thedevice is pulled such as through a vessel, the entrance thereto will notfall back or tip over. Moreover, the snare device maintains clearance inits interior space along its length allowing the material or objects toenter and be captured.

In one aspect of the invention, the snare is manufactured from a tubularelement to form struts (members run both generally longitudinally andgenerally circumferentially) with very small widths and thicknesses andrings (circumferential members) with very small widths and thicknessesbut large expansion ratios. The body of the snare device is defined by aplurality of openings bounded by generally longitudinally and generallycircumferentially extending members. A proximally extending member isattached to an elongate push member and the assembly is contemplated tobe used in conjunction with a generally tubular delivery catheter.

Overall, the intent of the invention is to provide a structure that hasthe capacity to engage and retain naturally occurring or foreign bodieswhile having a minimal profile that can traverse easily and repeatablythrough a standard microcatheter across tortuous anatomy. The deviceembodies superior flexibility to be deployed and retrieved consistentlyacross difficult anatomy while being able to retain captured material.The inner diameter of the device is heat-set to a pre-determined size.It is envisioned that there be a family of devices that have varyingstrut lengths, thicknesses, flexibility, and diameters as deemedappropriate for the specific type of vascular or non-vascular settingfor which the device is to be used.

In a presently preferred embodiment, the snare device is self-expandingand includes a midsection that forms a generally tubular profile. Theproximally extending member projects from a sidewall defining thegenerally tubular portion to thereby provide a substantiallyunobstructed radial opening at the proximal end of the snare. A terminal(i.e., distal) end of the snare device can be closed so as to form apocket for receiving emboli or thrombotic debris. In the event it isdesirable to employ a snare device manufactured from a tube embodyingboth proximal and distal open ends, a woven basket can be attached tothe distal end of the device.

The cut tube snare device can assume a number of forms. In one presentlycontemplated aspect, the snare device of the present invention embodiesfirst and second end portions, a pair of longitudinally spaced rings anda midsection defined by helically extending members. In another aspect,the intravascular snare device has a midsection defined by generallyparallel longitudinally extending members. In other aspects, the snaredevice includes a single convoluted ring or alternatively a body definedby a truncated stirrup-like structure. In yet another embodiment, thesnare device has a midsection including almond-shaped apertures asviewed perpendicular to the axis of the snare.

Moreover, the present invention embodies a tip for an endovasculardevice including an atraumatic soft coil for preventing damage to tissueand facilitates advanceability. The tip further includes multiple layersof coiled material to enhance these objectives as well as to providestiffness variations.

These and other objects and advantages of the invention will becomeapparent from the following more detailed description, when taken inconjunction with the accompanying drawings of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, partially in cross-section, of a vessel occludedby debris and a superior portion of a delivery catheter andintravascular snare assembly of the present invention positionedproximate the debris;

FIG. 2 is a side view, partially in cross-section, of the intravascularsnare of FIG. 1 deployed within the vessel;

FIG. 3 is a plan view depicting an unrolled pattern of an intravascularsnare of the present invention;

FIG. 4 is a plan view, depicting an unrolled pattern of an alternateembodiment of an intravascular snare of the present invention;

FIG. 5 is a plan view, depicting an unrolled pattern of a furtheralternate embodiment of an intravascular snare of the present invention;

FIG. 6 is a plan view, depicting an unrolled pattern of a fourthembodiment of an intravascular snare of the present invention;

FIG. 7 is a plan view, depicting an unrolled pattern of a fifthembodiment of an intravascular snare of the present invention;

FIG. 8 is a perspective view of the embodiment depicted in FIG. 7;

FIG. 9 is another perspective view of the embodiment depicted in FIG. 7;

FIG. 10 is an end on view from a proximal end viewpoint of theembodiment depicted in FIG. 7;

FIG. 11 is an end on view from a distal end viewpoint of the embodimentdepicted in FIG. 7;

FIG. 12 is a side view, depicting an elongate member of the presentinvention;

FIG. 13 is a side view, partially in cross-section, depicting aplurality of coils configured about a distal end portion of the elongatemembers in combination with a snare device of the present invention;

FIG. 14 is a cross-sectional view, taken along lines 14—14 depicting theassembly of FIG. 13;

FIG. 15 is a side view, partially in cross-section, depicting a distalend portion of a tip of the snare device of the present invention;

FIG. 16 is a cross-sectional view, taken along lines 16—16 of FIG. 15,depicting a portion of the assembly of FIG. 13;

FIG. 17 is a cross-sectional view, taken along lines 17—17 of FIG. 15,depicting the assembly of FIG. 13;

FIG. 18 is a plan view, depicting a portion of an unrolled pattern ofyet another embodiment of an intravascular snare of the presentinvention;

FIG. 19 is a perspective side view, depicting one step of amanufacturing process used to produce the snare device of FIG. 16;

FIG. 20 is a perspective bottom view, depicting one step of amanufacturing process used to produce the snare device of FIG. 16;

FIG. 21 is a side view, depicting an assembled snare device of FIG. 4 ofthe present invention including a braided structure for capturingemboli; and

FIG. 22 is a perspective view, depicting one manner of attachment of thebraided structure of FIG. 21 to a loop.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and in particular FIGS. 1 and 2, there isshown the snare device of the present invention. The snare device 20 isadapted to provide more consistent and improved radial opening as wellas enhanced angular resistance to collapse. Moreover, the snare device20 of the present invention is configured to facilitate the maintenanceof clearance in its interior space along its length allowing thematerial or objects to enter and be captured. Furthermore, since it iscontemplated that the snare device 20 be manufactured from a tubularmember to form elements with very small widths and thicknesses, thedevice is thus more easily packed to a relatively smaller diameter andinherently embodies high longitudinal flexibility.

The snare device 20 (FIG. 2) of the present invention includes a body 22having a proximal end portion 24 and a distal end portion 26. Theproximal end portion 24 is intended to be affixed to a terminal endportion of an elongate member 30 (described in more detail below). In apresently preferred embodiment, the body 22 of the snare device 20 isgenerally tubular with a proximally directed opening 32 and a generallyclosed terminal end 34 to thereby form a basket for receiving embolus,stones, thrombus and foreign bodies found in vasculature or other bodycavities.

The snare device 20 for intravascular uses is contemplated to be used inconjunction with a generally tubular delivery catheter 40, such as amicrocatheter. Additionally, it is contemplated that a conventionalguide catheter (not shown) be used in combination with the deliverycatheter 40 loaded with a snare device 20. The guide catheter isemployed to provide a guide within a patient's vasculature through whichthe delivery catheter 40 is inserted. A proximal end of the guideincludes a “Y” adapter fitted with sealing, hemostatic valves. The snaredevice 20 is intended to be self-expandable, however, it is possible toemploy an expandable member such as a balloon catheter (not shown) toradially expand a snare device that is not self-expandable, but rathermust be deformed to assume an expanded configuration.

In use, the body 22 of a snare device 20 is placed proximally in acompressed configuration coaxially within an internal bore of thegenerally tubular delivery catheter 20. The longitudinally extendingelongate member 30 which is attached to the proximal end 24 of the body22, is likewise coaxially received within the delivery catheter 40. Boththe body 22 and elongate member 30 are slidable within the deliverycatheter 40 and accordingly, the delivery catheter 40 and the snaredevice 20 can be displaced longitudinally with respect to each other.

A typical procedure will now be described. In order to restore patencyin a vessel, the snare device/delivery catheter assembly 42 isintroduced into a patient's vasculature using conventional means such asthe Seldinger technique. Sometimes, a cutdown is made to gain access tothe patient's vasculature. Using standard endovascular techniques, theemboli in the vasculature is located. The emboli is crossed with thedelivery catheter 40 and an appropriate guidewire (not shown). If thevessel is occluded, contrast is injected distal to the occlusion to mapthe distal vessels. The tip 26 of the delivery catheter 40 is positionedone device length or slightly more beyond the emboli. The guidewire isremoved and the snare device 20 is loaded through a rear hub (not shown)of the delivery catheter 20 with the assistance of a conventionalintroducer sheath (not shown). The snare device 20 is advanced 30-40 cmand the introducer sheath is then removed.

Next, the snare device 20 is advanced until the tip 26 of the basket isat the distal end of the delivery catheter 40. The snare device 20 isheld in place and the catheter 40 retracted to allow the device toexpand. Holding the snare device 20 in place, the catheter 40 is pulledback until it is proximal to the emboli 46. The entire system is drawnback holding relative positions between the snare device 20 and thecatheter 40, allowing the emboli 40 to enter the snare device 20. Thisstep can be assisted with a “stuttering” technique where the snaredevice 20 is drawn out a small amount, perhaps 1-2 mm, then the elongatemember 30 is advanced back perhaps 2 mm to flare the mouth of the snaredevice 20, assisting clot entry. Then the system is drawn out another 1mm. This is repeated until the device 20 has traversed a distance aboutits own length.

If the emboli is foreign in origin, such as a coil, the basket can bemoved back and forth past the coil in an iterative attempt to engage thecoil in the struts of the basket. When this has occurred, the catheter40 can be advanced and pinch the coil, locking it into one of theopenings of the basket. If the emboli is not radiopaque, its positioncan be checked by a contrast injection. Also, the radiopaque tip 26 ofsnare device 20 can be observed during this process. A pulsing motionindicates restored flow.

The system 42 is then drawn back until the distal end of a proximaldevice marker coil (described below) is at the tip of the guide. At thispoint, a large syringe, perhaps 60 cc, is attached to the guide catheterat the “Y” adapter on the hub. The guide catheter is aspirated as thesnare device 20 and clot 46 are drawn into the guide. Aspiration ismaintained until the snare device 20 is fully into the “Y” adapter ofthe guide catheter, but the snare device 20 is not yet drawn through thehemostatic valve. The “Y” adapter is detached and removed with the snaredevice in it, allowing a moment of bleed back through the guide to flushany loose clot. Optionally, then a second “Y” arm is attached to preventexcessive bleed back. The guide is then flushed with saline and theentire procedure repeated as required to remove further emboli.

The manner in which the body portion 22 of the snare device 20self-expands within vasculature and the resultant expansion profileprovides a number of advantages. In particular, the body 22 expands toconform to the repair site 44. That is, the generally tubular profile ofthe body portion 22 substantially conforms to the walls defining theblood vessel 49. Alternatively, the snare device 20 can be sized suchthat upon full expansion it has a diameter smaller than the diameter ofthe vessel if desired. Moreover, the expansion of the body 22facilitates the maintenance of clearance in its interior space along itslength allowing the material or objects to enter and be captured andspecifically provides a substantially unobstructed access to theproximally directed opening 32 to the body 22. Significantly, as thebody 22 self-expands, members 50, 51 leading to the opening 32 to thebody 22 are angled or oriented so as to be adjacent the walls definingthe blood vessel 49 and are therefore substantially removed from theflow path to thereby provide an unobstructed opening 32.

In its expanded state, the snare device 20 is particularly well-suitedto remove embolic or thrombotic debris 46 from the blood vessel 49. Asstated, the snare device 20 can be withdrawn proximally so that thedebris 46 can be captured by the body 22 of the snare device 20.Alternatively, a separate pusher mechanism (not shown) can be employedto push the debris 46 within the basket defined by the body portion 22.Once the debris has been captured, the snare device 20 and deliverycatheter 40 can be removed from the patient's vasculature or the snaredevice 20 containing the debris 46 can first be pulled within the guidecatheter (not shown) and then the assembly 42 removed from the targetrepair site 44. Also, just the proximal portion can be cinched down tolock the debris without being fully pulled into the delivery catheter40.

It is to be understood, however, that thrombus or other blood-basedmaterial captured within the snare may be eliminated in a variety ofways. For example, the material may be drawn into the guide catheterwith the aide of a vacuum applied to the guide catheter, and removedfrom the body. Also, these materials may be removed from the occludedvessel and allowed to dissolve under natural or induced lytic processes.Alternately, the blood-based material may be inserted into othervasculature more tolerant of occlusion and released.

Referring now to FIG. 3, there is shown one preferred pattern 52 of thesnare device 20 of the present invention. As will be developed furtherbelow, it is contemplated that the snare pattern 52 be cut from atubular member using a laser. As best seen in its flattened or unrolledstate, the snare pattern 52 composes a body 22 including proximal anddistal end portions 24, 26, a midsection 54 and an elongate member 30extending proximally from the proximal end portion 24.

The proximal end portion 24 includes members or leashes 50 which lead toand aid in defining an opening to the body 22, when in its as cutconfiguration. The proximal end portion further embodies a pair ofconnectors 51 extending at an angle from the leashes 50 to therebyaccomplish offsetting elongate member 70 from a central axis of the ascut tubular body 22 of snare device 20 as best seen in FIGS. 2 and 8.The connectors 51, in turn, converge to form a proximally directed tab53 that is connected to the elongate member 30. The leashes 50 andconnectors 51 define a centrally located, generally diamond-shapedaperture 56, having a first length, that is substantially sandwichedbetween two parallelogram-shaped, proximal apertures 58 having arelatively shorter second length. A proximal convoluted ring 60 definedby members 61 arranged in a generally sinusoidal pattern is locateddistally adjacent the proximal end portion 24. The ring 60 provides foroptimal radial opening of the basket-like body 22.

The distal end portion 26 of the snare pattern 52 includes members orleashes 66 which define an open ended, distally directed triangle 68sandwiched between a pair of two, parallelogram-shaped, distal apertures70. A distal convoluted ring 72 defined by members 73 arranged in agenerally sinusoidal pattern is located proximally adjacent the distalend portion 26. The ring 72 additionally provides for maximal radialopening of the body 27. Distally directed extensions 78 project, in aparallel fashion, from pairs of converging leashes 66.

The midsection 54 of the snare pattern 52 includes a plurality ofgenerally parallel longitudinally extending members 84, each of whichare joined at an angle and at one end, respectively, to the proximalring 60. The other end of these members are joined at an angle to thedistal ring 72.

In its as cut form, the terminal ends 80, 82 of theparallelogram-shaped, distal apertures 70 are joined together to form asubstantially closed basket. This structure can be joined usingsoldering or by employing a coil (described hereinbelow) that is wrappedabout adjacent structures to form a soft tip. Distally directedextensions 78 may be trimmed to a desired length. The longitudinallyextending members 84, while maintaining a parallel relationship, eachdefine a helical pattern to thereby form a generally tubular midsection54. The helical configuration provides flexibility around bends as wellas good foreign body containment. The members 50 form a tapered openingto the generally tubular midsection 54 with the elongate member 30extending proximally from a sidewall defined by the midsection 54. It iscontemplated that the resultant tubular structure, in an undeformedstate, includes a longitudinal axis that is parallel to both theelongate member 30 and the distally directed projections 78.

In an alternative embodiment of a snare pattern 90 (FIG. 4), theproximal end and distal end portions 24, 26 also include members 50, 51,66 which define proximal and distal parallelogram-shaped apertures 58,70 as well as a diamond-shaped aperture 56 and an open ended triangle68. This second snare pattern 90 also similarly includes proximal anddistal rings 60, 72 as well as distally directed extensions 78, each ofwhich are joined to one of the distal parallelogram-shaped apertures 70.Moreover, the midsection 54 of the pattern 90 includes a plurality ofparallel, longitudinally extending members 84 which are joined to thestructure defining the proximal and distal end portions 24, 26. Thisembodiment differs from the first embodiment, however, in that thelongitudinally extending members are not helically configured when thepattern 90 is in its as cut form. Rather, while defining a sidewall of agenerally tubular midsection 54, each of the longitudinally extendingmembers 84 are parallel to a longitudinal axis of the resultant tubularsnare device 20. Being so arranged, the midsection 54 possesses thenecessary flexibility to traverse sharp bends in anatomy as well as thecapability of being packed into a small profile with minimal bulk.

Further, it is to be recognized that as with the first embodiment, asubstantial closed-ended basket is formed by joining via conventionalmeans the terminal ends 78 of the snare pattern 90. Additionally, atapered opening to a generally tubular midsection 54 is provided by theproximal end portion 24 where the elongate member 30 extends proximallyfrom a sidewall defined by the midsection 54.

Although each of the proximal and distal rings 60, 72 are shown asembodying a four crown design, fewer or more crowns are contemplated.Moreover, there need not be a leash 50, extending from each crown. It isnecessary, however, that as with the ring design depicted, the modifiedpattern also result in rings that provide complete open deploymentconsistently and reliably. To wit, such rings do not fall back. That is,there is no angular deflection when the structure is pulled into a clotor foreign body.

Turning now to FIG. 5, in yet another embodiment of the snare device 20of the present invention, a third snare pattern 100 includes a pluralityof almond-shaped apertures 102 configured both circumferentially andlongitudinally along the snare pattern 100. Each almond-shaped apertureincludes curved members 104 shared by adjacent circumferential andlongitudinal almond-shaped apertures 102.

The third snare pattern 100 additionally includes an elongate member 30extending proximally from a pair of converging, undulating members 105that lead to a first pair of circumferentially spaced, almond-shapedapertures 106 defined by curved members 104. Each of the first pair ofcircumferentially spaced, almond-shaped apertures 106 are joined andshare a portion of a sidewall 104 of two of four almond-shaped aperturesdefining a first ring 108 of almond-shaped apertures. In a presentlypreferred embodiment, a series of three additional nested rings 110 ofalmond-shaped apertures 102, though fewer or more are contemplated,complete a midsection 54 of the third snare pattern 100. Extending fromterminal ends 112 of each almond-shaped aperture 102 of the distal mostring 110, is a distally directed extension 114.

In its manufactured form, the third snare pattern 100 has a midsection54 that defines a generally tubular shape and a closed basket is formedby joining the terminal ends 112 of the most distal ring of apertures110. Again, the terminal ends may be joined using soldering, laserwelding, adhesive, shrink wrap, or by employing a coil configured aboutadjacent structure.

Additionally, the resultant structure includes a tapered opening to thetubular midsection 54 where the elongate member 30 extends proximallyfrom a sidewall defining the tubular midsection 54 and where theelongate member 30 and distally directed members 114 are each parallelto a longitudinal access of the resultant snare device 20. The distallydirected members 114 can be trimmed to a desired length. An additionalfeature of this embodiment (and FIG. 7 described below) is that thecurved transitions from tab 53 to converging, undulating members 105enhances ease of retrieval of the device into a microcatheter.

In a fourth embodiment (FIG. 6), the snare device 20 embodies a snarepattern 120 that includes a single conventional ring 122 defined by acontinuous set of interconnected members 124. The interconnected members124 are composed of straight struts that together define a central lumenin the manufactured form. The members 124 converge at ends thereof toform four proximal and distal crowns or vertices 126, 127 on each sideof the ring 122. The ring 122 serves as a central body 128 of the snaredevice 20.

A single member 130 extends from each of the four crowns 126, 127 of thering in both proximal and distal directions. Proximally, the fourmembers 130 converge into two members 132, which again converge into asingle member 134. This single proximal member 134 serves as a tab forattachment to the elongated member 30.

Extending from each of the members 130 projecting from the distal crowns127 is a single distally directed extension 136. The distally directedextensions 136 can be configured to form an atraumatic tip as describedherein below.

In a fifth embodiment (FIG. 7), the snare device 20 has a pattern 140similar to that of the fourth embodiment. In particular, this patternalso includes a convoluted ring 142 defined of a continuous set ofinterconnected members 144. The interconnected members 144 are composedof straight sections that together form a central lumen 146 (see FIGS.8-11) in the manufactured form. The members converge at terminal endsthereof to form four proximal and distal crowns 147, 148 on each side ofthe ring 142, which serves as a central body 150 of the device 20. Inthis embodiment, however, alternative crowns 147, 148 at each end of thering 142 are offset longitudinally from each other. Thus, every otherinterconnecting member 144 has a different length.

As with the fourth embodiment, a single member 152 extends from each ofthe four crowns 147, 148 in both proximal and distal directions.Further, the four members 152 connected to the proximal crowns 147converge into two members 154, each of which again converge to form aproximal tab 156. At the distal end of the device 20, adjacent pairs ofthe single members 152 converge to a single extension 158. Again, theterminal ends 158 may be joined using soldering, laser welding,adhesive, shrink wrap, or by employing a coil configured about adjacentstructure.

Referring now to FIG. 12, there is shown one preferred embodiment of theelongated member 30 of the present invention. The member 30 embodies agradual or step-tapered core comprising a proximal section of 304Vstainless steel and a distal section of nitinol or an equivalentmaterial for the intended purpose. A proximal portion 160 of the member30 has a generally constant cross-sectional profile and a first diameter161. At a transition point 162, the member 30 begins to taper in agradual and consistent, alternatively in a step-tapered manner, from thefirst diameter 161 to a second diameter 163 along a distal end portion164.

As shown in FIGS. 13 and 14, a pair of longitudinally adjacent arrangedcoils 166, 168 are employed to attach a proximal tab 174 of a snaredevice 20 to the distal end portion 164 of the elongate member 30. Thefirst, proximal coil 166 is contemplated to be composed of 304Vstainless steel, the first coil being soldered to the elongate wire 30near its tapered portion 170. The second coil 168 is contemplated to becomprised of about 90% platinum and 10% iridium alloy. This second coil168, which serves as a radiopaque marker, is soldered to the elongatemember 30 near a distal end portion 172 of the first coil 166.Alternatively, the second coil 168 is soldered to the first coil 166. Aproximal tab 174 of the snare device 20 is contained within the secondcoil 168 and is soldered 176 to the elongate member 30.

Turning now to FIGS. 15-17, one presently preferred embodiment of adistal tip portion 180 of the snare device 20 of the present inventionis described. The distal tip portion 180 is comprised of two partiallycoaxial coils 182, 184, the combination of which retains the extensionsprojecting from the body of the snare device 20. The combination alsoprovides a soft atraumatic tip with variable stiffness from softestdistally to stiffer proximally.

The inner coil 182 is comprised of nitinol or equivalent material, andbegins at a proximal location 186 and extends to a distal location 188.The nitinol inner coil 182 provides kink resistance as well as creates asmooth stiffness transition from the tip of the basket portion of thesnare device 20. The outer coil 184 is coaxially configured about adistal portion 190 of the inner coil 182 and is preferably comprised of90% platinum and 10% iridium alloy or an equivalent combination ofmaterials. As such, the outer coil 184 can operate as a radiopaquemarker.

The distal tip portion 180 further includes a rounded terminal end 192that provides a blunt atraumatic surface. The terminal end 192 embodiesa soldered joint which acts in retaining the helical configuration ofthe outer coil 184.

With reference to FIGS. 18-20, a brief summary of the process used tomanufacture the snare devices 20 of the present invention is provided,with a specific focus on a sixth embodiment of the present invention. Asshown in FIG. 18, the sixth embodiment is relatively similar to atruncated third embodiment and defines a general stirrup-shaped pattern220. This stirrup pattern 220 also includes a proximally directed tab221 and a pair of diverging members 222 extending from the tab 221.Configured at each terminal end 224 of the diverging members 222 is asingle almond-shaped aperture 226 defined by curved members 228. Thecurved members 228 further include apices 229, 230 defining outer edgesof the curved member 228. Moreover, joined to a distal end 232 of eachalmond-shaped opening 226 is a distally directed extension 234.

It is contemplated that the snare devices 20 of the present invention becut from a tube 235 (FIGS. 19 and 20) using conventional means such as alaser. In particular, a specific pattern is programmed into the laserdevice and the laser is activated to cut the desired pattern into thetubular element 235. The excess tubular components are removed, therebyleaving a manufactured structure such as the stirrup snare pattern 220shown in FIGS. 19 and 20, corresponding to the desired pattern. In apresently preferred embodiment, a super elastic material such as nitinolis a material of choice for the snare device 20. Thereafter,post-processing such as surface treatment, burr removal and deformationof the manufactured structure is performed. Heat treating is alsoperformed for sizing the device.

In particular, post-processing steps include taking an as-cut device andbead blast the device with aluminum oxide blasting media. The device isthen inspected under a microscope for residual slag. If slag remains,the device is bead blasted again. Thereafter, the device is heat-treatedin a molten salt bath without expanding. The device is subsequentlyheat-expanded in a molten salt bath mounted on a suitable size mandrel.After heat expansion, surface oxidation is removed in an aqua regiabath. When nitinol is the material of choice, the nitinol is etched withHF solution to desired softness or strut size. The device is thenmounted on a guidewire.

In the case of the stirrup pattern 220, the post-processing may includedeforming the pattern 220 and then joining together the distal endmembers 234 as well as adjacent apices 229, 230 for the purpose ofachieving a closed basket for receiving debris found in vasculature.Being so configured, the pair of diverging members 222 define an openingto the resultant basket and the elongate member 30 extends from asidewall defined by the pocket. Alternatively, distal end members 234can be left apart and a basket attached to them as described below.

It is contemplated that certain circumstances may dictate other forms ofa snare device 20. In particular, it is contemplated that a braidedstructure can be attached to a distal end portion of any of thepreviously described snare patterns. A braid can also be attached alongthe length of the body of the snare device. As shown in FIG. 21, onesuch braided structure 250 can be attached to, for example, a distal endportion 26, as well as the body snare pattern 90. In such a case, ratherthan terminating with distally directed members 78, the snare device 20can include terminal apices 252 forming loops 254.

In one presently preferred embodiment, members 256 defining a first end258 of the braided structure 250 can be attached to the loops 254 of theterminal apices 252 by conventional means. A second end 260 of thebraided structure 250 can remain in an open configuration, oralternatively, members 256 defining the second end 260 can be joined toform a closed elongated tube.

The snare/braid assembly provides a number of advantages. In particular,such an assembly embodies additional volume for collecting debris fromvasculature. Additionally, the braided structure includes sidewallscharacterized by a higher density which can, in certain circumstances,be better suited for capturing relatively smaller debris found invasculature.

Turning to FIG. 22, it is important that the leading edges 262 of theconnection between the braided structure 250 and the loops 254 formed inthe distal end portions of a snare pattern be as atraumatic as possible.In one presently preferred embodiment, the members 250 defining a firstend 258 of the braided structure 250 are configured into a two-leggedcoil 263 routed such that legs 264 of the coil extend from an outersurface of the loops 254 formed in the distal end portion 26. The coilis heat-set to enhance the connection to the snare pattern. It is alsocontemplated that single-leg coils (not shown) could additionally beused for attachment in the event forces required to unravel thesingle-leg coil are greater than the force necessary to deploy andretract the braided structure 250. An atraumatic leading end, however,remains an objective, as well as space considerations (i.e., low profilefor packing into microcatheter).

The snare devices of the present invention compared to prior art loopsnares each provide improved radial opening since in an expanded state,the elongate member 30 is positioned substantially out of the flow path.Additionally, the device embodies improved resistance to radial loadscompared to prior art loop snares. Moreover, since less deformation isrequired to produce a desired snare pattern, in that, angles betweenmembers are provided by laser cutting rather than from localdeformations, for example, there is improved stress distribution alongthe snare devices of the present invention compared to prior art loopsnares. Additionally, a greater reduction in radial profile can beachieved without sacrificing performance and in particular, the devicecan be used in conjunction with microcatheters. As such, the snaredevices 20 of the present invention can be passed through narrow andtortuous vasculature. The applications of the present invention are morewidespread than that of conventional snare devices because of greaterretrieval characteristics while retaining the deliverabilitycharacteristics.

The above described invention is principally conceived to be operationalfor use in engaging for the purpose of displacing and/or removingmaterial either foreign or native to the body, including partial orcomplete obstructions embolic and/or thrombotic in nature, fromintraluminal or extraluminal spaces of the body including but notlimited to intravascular and/or intra-arterial regions of theneurovasculature, as well as tubings, stents, or other objects that mayor may not be internal to the body. The purpose of the device is torestore functionality of the luminal space or systems dependent on theparticular luminal space or as a method of producing any desired effectassociated with the removal or displacement of undesirable material.

The intended delivery of the disclosed invention is by means of acommercially available catheter selected to its ability to access thedesired location of engagement. The invention may be optimized forspecific locations or uses by means of sizing the individual elements inthe design and/or the overall dimensions, as well as selection ofmaterials, mesh configuration, number and relative geometry of componentmembers to meet the requirements of the operational space. Optimizationsmay include tabs protruding from the sides of members to increasecoverage of the open areas between members, offsetting vertices ofjoints to increase packing efficiency, or providing unconnected distalcurved path. There may additionally be variations of the dimensions oflength, thickness, and width of distal and proximal tabs for joiningbasket with delivery wire and distal tip to provide smooth stiffnesstransitions from tip to basket and basket to delivery wire. Suchoptimizations are means of adjusting operational attributes including:flexibility, applied circumferential force, engagement effectiveness,deliverability and traversal through tortuous vasculature, and volume ofmaterial to be engaged.

Alternate or additional materials for the basket portion of the devicemay include a thermoset, elastomer, thermoplastic constituents such asnylon, or other metal either pure or alloyed, as well as compositematerials such as a combination of glass, aramid, or carbon in a bindingmatrix. A secondary mesh of the same or dissimilar material may be addedto the basket. The wire portion of the device can alternatively be madefrom a single metal or combination of metals for kink resistance andhigh flexibility. Either or both components may be tapered to give atransition in stiffness that is appropriate for the vessel in which theinvention is to be delivered. The distal tip of the device mayincorporate concentric coils made of nitinol, stainless steel, or othermetal or plastic to provide a soft flexible atraumatic end.

An alternate method of manufacture of the basket portion of the devicemay be etching, or metal or polymer injection molding. Furthermore, thedevice may employ any combination of coatings, agents, or featuresincluding those of that result from material addition or subtraction tocreate grooves, bumps, three dimensional patterns, and textures on innerand/or outer surfaces or any combination thereof to promote desiredproperties such as adherence of materials to be engaged, radiopacity,and low friction between the device and the vessel wall or microcatheterlumen.

In summary, the invention is deliverable to remote regions of theneurovasculature by gaining access through the use of a guidewire andmicrocatheter in the vasculature and subsequent deployment of theinvention through the lumen of the microcatheter. In a vessel in whichflow is impeded or obstructed by material and/or objects including thoseformed by the body such as blood clot, the device is deployed bywithdrawing the microcatheter relative to the wire. Engagement occurs asthe system composed of the invention and microcatheter is pulled intothe material. After the material has been engaged, removal of thematerial is accomplished by withdrawing the system into a guide catheterlumen through which the microcatheter is passed with or withoutsimultaneously pulling fluid through the guide lumen.

Thus, it will be apparent from the foregoing that, while particularforms of the invention have been illustrated and described, variousmodifications can be made without the parting from the spirit and scopeof the invention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1. A method involving a snare device for use within vasculaturecomprising, configuring the snare device to capture material foundwithin vasculature by providing the snare device with a body portionmanufactured from a tube, the body portion attached to an elongatemember; placing the snare device within vasculature so that a portion ofthe elongate member extends exterior vasculature; and capturing materialin the body portion of the snare device.
 2. The method of claim 1,wherein said configuring step further includes positioning the snaredevice within vasculature of a patient.
 3. The method of claim 2,further comprising the step of providing a guide catheter and allowing amoment of bleed back from the vasculature and through the guide catheterto flush any loose undesirable material.
 4. The method of claim 3,wherein the guide catheter includes a detachable adaptor and furthercomprising the step of attaching a supplemental adapter to the guidecatheter.
 5. The method of claim 4, further comprising the step offlushing the guide catheter with saline.
 6. The method of claim 1,wherein said configuring step further includes positioning the snaredevice within intracranial vasculature of a patient.
 7. The method ofclaim 1, wherein said configuring step further includes positioning thesnare device distal of a blood clot within intracranial vasculature of apatient.
 8. The method of claim 1, further comprising configuring thesnare device in an expanded condition.
 9. The method of claim 1, furthercomprising enclosing material within the body portion.
 10. The method ofclaim 1, further comprising: configuring the snare device to beslideably received within a guide catheter that includes a detachableadaptor; withdrawing the snare device to a position adjacent an openingto the guide catheter; aspirating the guide catheter while withdrawingthe snare device into the guide catheter; maintaining aspirations untilthe snare device is positioned within the adaptor; and detaching theadaptor, with the snare device contained therein, from the guidecatheter.